Prepare Fondant Legs: Start by mixing CMC powder into orange fondant, kneading until well incorporated. Roll the fondant into thin strips to create witch legs, cutting them into desired lengths. Shape them and add black fondant stripes for detail. Keep the fondant covered to prevent it from drying out while you proceed with the next steps.

Bake the Cake: Preheat your oven to 170°C (340°F). In a large mixing bowl, cream together the unsalted butter and granulated sugar until light and fluffy, about 3–5 minutes. Gradually add in the eggs, mixing well after each addition. Sift together the self-raising flour and cocoa powder, and slowly combine with the wet ingredients until just mixed. Pour the batter into a greased 9-inch square baking tin and bake for 45–50 minutes, or until a toothpick inserted into the center comes out clean.

Cool the Cake: Once the cake is baked, remove it from the oven and allow it to cool in the tin for 10 minutes. Carefully transfer the cake to a wire rack and let it cool completely. This cooling process is essential; frosting on a warm cake can melt and affect the layers in your Witches' Brew Halloween Cake Jars.

Make the Buttercream: While the cake is cooling, prepare the vibrant green buttercream frosting. In a mixing bowl, beat the unsalted butter until creamy and smooth. Gradually add powdered sugar, continuing to mix until fully combined. Stir in vanilla extract and gel food coloring until desired shade is achieved, ensuring it matches the theme of your Witches' Brew Halloween Cake Jars.

Assemble the Jars: With the cake cooled and buttercream ready, cut the chocolate cake into rounds that fit inside your jars. Layer the cake and buttercream in each jar, alternating between the two and adding festive sprinkles for a fun touch. Once you’ve created your delightful layers, insert the fondant witch legs into the top of each jar, positioning them to give a charming ‘peeking out’ effect, creating the allure of Witches' Brew Halloween Cake Jars.